1. Field of the Invention
The present invention relates to a mobile communication system, and more particularly, to a mobile terminal, system and method for restricting access to an enhanced services system.
2. Description of the Related Art
Evolution-Data Optimized (EVDO), also referred to as Evolution-Data Only, is a wireless radio broadband data standard for high data rate communication. As demand for high data rate services, such as Video On Demand (VOD) and Music On Demand (MOD), is increasing, EVDO systems are increasingly being deployed with pre-existing voice networks, such as 1× networks. Although 1× networks are capable of providing data communication, they are optimized for voice communication and cannot provide the high data rates which EVDO systems provide.
In an EVDO system, the overall throughput of the system depends on the number of users communicating with the system. Thus, the data rate available to any one user depends on the number of other users using the system. Further, when a large number of users simultaneously transmit data to a base station of an EVDO system, there is a large amount of uplink interference, which lowers the available data rate for all users.
Since interference is generated each time a user communicates with an EVDO system, there is a need to prevent non-authorized users from communicating with an EVDO system. Non-authorized users may include, for example, users who are not subscribers to the EVDO system, subscribers who have not paid their bills, and subscribers whose subscription period has expired.
FIG. 1 is a flow chart showing a conventional method performed by a mobile terminal when it attempts to access an EVDO system.
As illustrated in FIG. 1, a mobile terminal is first powered on (S102). If the mobile terminal is located in a service area of a 1× system and an EVDO system, an initialization process is performed by the mobile terminal to obtain service from the 1× system and the EVDO system (S104). The mobile terminal then enters into a standby mode (S106). When a mobile terminal user attempts to use the EVDO system (S108), the EVDO system determines whether the user is an authorized user of the EVDO system (S110), for example, by comparing a subscriber identifier associated with the mobile terminal with a list of authorized subscriber identifiers. If the user is authorized, the user is provided access to the EVDO system (S112). After the user finishes using the EVDO system (S114), the mobile terminal returns to the standby mode (S106).
However, if the EVDO system determines that the mobile terminal user is not an authorized user of the EVDO system (S110), the system reports an authentication failure to the mobile terminal (S116), which keeps track of the number of times an authentication failure has occurred. The mobile terminal then determines whether an authentication failure has occurred more than a predetermined number of times (typically, three) (S118). If the mobile terminal determines that an authentication failure has occurred more than the predetermined number or times, the mobile terminal then loses its service from the EVDO system (S120). However, after the passage of a predetermined amount of time (typically, between three and ten minutes), the mobile terminal once again performs an initialization process to re-obtain service from the EVDO system (S122).
According to the process described above, when an unauthorized user attempts to use the EVDO system, the EVDO system must perform processes to determine whether the user is authorized. Even when the EVDO system determines that a user is unauthorized, the EVDO system must later perform these processes again if the user later attempts to use the EVDO system again. The signaling exchanged between the mobile terminal and a base station of the EVDO system every time the user attempts to use the EVDO system increases the load on the EVDO system, wastes wireless resources, and causes unnecessary interference to other users.
Moreover, even when a user who is not an EVDO subscriber uses the 1× system instead of the EVDO system to perform data communication, the user's mobile terminal continues to monitor the EVDO system when it is in service, which unnecessarily consumes power from the mobile terminal's battery.